MVRefreshDataViewController.m

#pragma mark Private methods
- (void)refreshData
{
    [self setMessages:[[NSArray alloc] init]];

    for (MVAccount *account in [[self accountManager] allAccounts])
    {
        MCOIMAPSession *session = [[MCOIMAPSession alloc] init];

        [session setHostname:[account imapServer]];
        [session setPort:(unsigned int) [account imapPort]];
        [session setUsername:[account username]];
        [session setPassword:[account password]];
        [session setConnectionType:[account tls] ? MCOConnectionTypeTLS : MCOConnectionTypeClear];

        MCOIMAPFetchFoldersOperation *fetchFoldersOperation = [session fetchAllFoldersOperation];

        [fetchFoldersOperation start:^(NSError *foldersError, NSArray *folders)
        {
            for (MCOIMAPFolder *folder in folders)
            {
                NSLog(@"FOLDER: %@", [folder path]);
                MCOIndexSet *indexSet = [MCOIndexSet indexSetWithRange:MCORangeMake(1, UINT64_MAX)];
                MCOIMAPFetchMessagesOperation *fetchMessagesOperation = [session fetchMessagesByUIDOperationWithFolder:[folder path] requestKind:MCOIMAPMessagesRequestKindFullHeaders uids:indexSet];

                [fetchMessagesOperation start:^(NSError *error, NSArray *messages, MCOIndexSet *vanishedMessages)
                {
                    NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"header.date" ascending:NO];

                    NSLog(@"MESSAGE: %@ (IN FOLDER %@)", [messages sortedArrayUsingDescriptors:@[sortDescriptor]], [folder path]);
                }];
            }
        }];
    }
}